0Spam.com - A Virtually 100% Effective Free Anti Spam Service is a complete piece of crap. Nope, I don't use'em. I'm just abused by them.
One of the many worms out there is sending its crap and spoofing the From with my email address. We all know it happens, right? Well, these idiots don't bother to check to see if it's bogus email, instead, they send an automatic verification email to me, for me to prove that I really sent the mail. 30 times. For the same recipient. Of course, they provide no way to anti-verify it. So, I continue to get assloads of their verification mails in my inbox. Helping to solve the spam problem? Not from my perspective.
update
Just received a reply to my complaint...
OK, your address is now blocked. You could have setup filters in your mail client to block us as well.
Doesn't that seem like an odd response to someone providing services to keep your inbox clean? Not even an opt-out response, but more of a "just delete'em" response. Yep, idiots.
Well I guess it's effective for them! Maybe not so nice for you.
You should have setup an out-of-office auto-reply for their address!